Using an optical Cable keep everything digital. By using an RCA cable the signal is outputting analog and converted to digital. Sometimes I like to keep it all digital if the music is digital and analog if it is analog, if I can. Some people, me included, like Converting CD music which is digital to analog, by using RCA jacks. Some say that the music sounds better. It may sound better to you or you may not be able to tell the difference by doing it the way I mentioned. Enjoy your music!